This invention relates to metal working operations, and, more particularly, to die tooling with improved resistance to wear.
Many metallic articles are formed to their final shapes and sizes by metal working techniques. In one such technique, a thin metal article is formed from a sheet or coiled strip metal workpiece using a metal forming die. The die is another piece of material having a preselected shape that aids in the forming of the workpiece into its intermediate or final shape. Sheet workpieces are commonly formed by forcing the sheet into a female die using a male die.
Some of the die forming operations involve large tonnages of metal workpieces and produce familiar products. For example, most automobiles have metallic body panels. To fabricate those panels, flat pieces of metal sheet are formed by placing the starting sheet over a female die, and then forcing the sheet into the female die with an appropriately shaped male die. The resulting part has the complex shape of the body panel.
The life of dies is normally limited by wear that causes changes in their dimensions and thence to the dimensions of the finished parts. As each part is formed, the friction between the sheet workpiece and the die removes some small amount of material from the die. Eventually, the die is so changed in dimension that the final products do not meet the dimensional standards.
In production operations, the dies are made from specialty steels or other ferrous-alloy materials that are very hard and wear resistant compared with the articles produced using these dies. Such dies can be used to form thousands of individual parts. These dies used in production operations are typically expensive to manufacture for a number of reasons, including the difficulty in machining hard materials and the need to perform extensive surface treatments.
There is an economic incentive in the manufacturing industry to replace expensive ferrous-alloy tool and die materials with less expensive non-ferrous materials. These non-ferrous materials can be zinc-based or aluminum-based metals or even non-metallic materials such as plastic or epoxy. The problem, however, is that all of these non-ferrous materials exhibit reduced wear life compared to ferrous materials. The use of non-ferrous materials has therefore been limited to prototype fabrication or limited production runs where it is not necessary that the die perform to produce thousands of parts. For the non-ferrous die materials to have production applications, techniques must be developed to extend their wear life.
There is therefore a continuing need for improved non-ferrous die materials, which are inexpensive and have acceptable wear-life characteristics. The present invention fulfills this need, and further provides related advantages.